JPS62128229A - Optical amplifier - Google Patents

Abstract

PURPOSE:To amplify a light with a high accuracy and comparatively simple constitution by providing a beam splitter branching the output light of an electrooptic conversion means, applying a part to the 1st optical frequency conversion means and converting the remaining light into an output light in response to the quantity of an input light fed to the 2nd optical frequency conversion means. CONSTITUTION:The static capacitance of the depletion layer of a photodiode PD constituting optical frequency conversion means 1, 2 is increased as the quantity of input light is increased and oscillated frequencies f1, f2 are lowered as the static capacitance increases. The output signal of the optical frequency conversion means 1, 2 is fed to an up-down counter 3, where the difference of the frequencies f1, f2 is counted and outputted. A drive circuit 4 drives a light emitting diode 5 in response to the count output and its light emitting intensity is changed in proportion to the polarity and the amplitude of the count output. Since a part of the output light of the light emitting diode 5 is fed to the junction of the photo diode PD constituting the 1st optical frequency conversion means 1 via a beam splitter 6, the diode is in drive control to have the relation of f1=f2 and the input light IN is amplified in response to the transmitted light to the reflected light of the beam splitter 6.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical amplifier.

[Background Art] For example, in optical transmission, it is necessary to amplify light at a relay point.

Conventionally, when amplifying light in this way, the light is first converted into an electrical signal using a photoelectric converter such as a photodiode, the converted electrical signal is amplified, and the amplified electrical signal is 2. Description of the Related Art Driving light emitting devices such as il photodiodes is being practiced.

[Problems to be solved by the invention] However, according to such a conventional configuration, when focusing on the degree of amplification of light, it is not only the gain of the amplifier that amplifies the electrical signal, but also the conversion of the light receiving element and the light emitting element. It has the disadvantage that it varies greatly due to variations in efficiency.

Furthermore, the conversion efficiency of each of these elements is greatly affected by temperature and is extremely unstable.

The present invention has been made with attention to these points, and its purpose is to provide an optical amplifier that can amplify light with high precision with a relatively simple configuration. I! It is about providing.

[Means for Solving the Problems 1] The present invention achieves the above object by using a first semiconductor substrate which is integrated on the same semiconductor substrate and has the same conversion characteristics for converting the amount of light into a frequency. a second optical frequency conversion means; Second
a comparing means for comparing the conversion frequencies of the optical frequency converting means; an electro-optic converting means for changing the amount of output light according to the comparison result of the comparing means; The present invention is characterized in that it comprises a beam splitter which outputs Iζ light in accordance with the Pano J optical frequency, which is added to the first optical frequency converting means and the rest is added to the second optical frequency converting means.

[Example] Embodiments of the present invention will be described in detail below with reference to the drawings.

The figure is a block diagram showing the main parts of an embodiment of the present invention. In the figure, 1 and 2 have the same conversion characteristics for converting the amount of light into frequency. This is an oscillation circuit used as a second optical frequency conversion means, and is configured so that the oscillation frequency changes according to a change in capacitance caused by the amount of light incident on, for example, a photodiode (PI). In addition, these 1st. The second optical frequency conversion means 1 and 2 are integrated as an integrated circuit on the same semiconductor substrate. 3 is the first of these
, the output frequencies f, , f2 of the second oscillation circuit 1.2, and uses an up/down counter, for example. 4 is a drive circuit that drives the electro-optical conversion means 5 according to the count output of the up/down counter 3; for example, D
A device consisting of a /A converter and an integrator that integrates the D and /A conversion outputs is used. As the electro-optical conversion means 5, for example, a light emitting diode is used. 6 branches the output light of this electro-optical converter 5 and adds a part to the photodiode PD constituting the first optical frequency converter 1, and the rest to the photodiode PD constituting the second optical frequency converter 2. Output light 0LJT according to the amount of input light applied to the PD
It is a beam splitter that outputs as follows. As such a beam splitter 6, for example, a half mirror is used.

The operation of the circuit configured in this way will be explained.

When the input light IN is applied to the junction surface of the photodiode PD constituting the second optical frequency conversion means 2, the capacitance of the depletion layer changes according to the amount of input light, and the second optical frequency conversion means 2 It oscillates at a frequency f2 corresponding to its capacitance. On the other hand, a part of the output light of the light emitting diode 5 is applied to the junction surface of the photodiode PD constituting the first optical frequency conversion means 1 via the beam splitter 6, so that the depletion layer becomes static depending on the amount of input light. The capacitance changes,
The first optical frequency conversion means 1 oscillates at a frequency f depending on its capacitance. The capacitance of the depletion layer of the photodiode PD constituting each of these optical frequency conversion means 1 and 2 increases as the amount of light input to the junction surface increases, and each oscillation frequency fl+f2 increases as the capacitance increases. decrease accordingly. The output signals of each of these optical frequency conversion means 1 and 2 are added to an up/down counter 3, and the difference between the frequencies f, , f2 of the Ryokawa power signals is counted and output. The drive circuit 4 is
The light emitting diode 5 is driven according to the count output of the up/down counter 3. The light emission intensity of the light emitting diode 5 changes in proportion to the polarity and magnitude of the count output of the up/down counter 3.

Here, as described above, a part of the output light of the light emitting diode 5 is applied to the junction surface of the photodiode PD constituting the first optical frequency conversion means 1 via the beam splitter 6, so that f, The drive will be controlled so that -f2 is achieved.

As a result, the input light IN applied to the junction surface of the photodiode PD constituting the second optical frequency conversion means 2 is
The light is amplified according to the ratio of the transmitted light and the reflected light of the beam splitter 6. That is, for example, if the ratio of transmitted light and reflected light of the beam splitter 6 is set to 10:1, the input light IN will be amplified ten times and output as the output light OLJT.

According to such a configuration, the first . Since the second optical frequency conversion means is integrated on the same semiconductor substrate, it is not affected by variations in conversion efficiency or temperature changes, and furthermore, the degree of amplification of light is the same as that of transmitted light and reflected light at the beam splitter. It is determined only by the ratio of , and extremely stable optical amplification characteristics can be obtained.

d3, the electro-optical conversion means is not limited to a light emitting diode, and may be a semiconductor laser, for example.

In addition, the beam splitter is not limited to a half mirror formed by depositing a metal thin film on a transparent substrate, and may also be a prism. Alternatively, it may be a guiding waveguide integrated into the same substrate as the optical frequency conversion means.

[Effects of the Invention] As described above, according to the present invention, an optical amplifier that can amplify light with high accuracy with a relatively simple configuration can be realized, and the practical effects are great.

[Brief explanation of drawings]

The figure is a block diagram showing one embodiment of the present invention. 1.2... Optical frequency conversion means, 3... Frequency comparison means, 4... Drive circuit, 5... Electro-optical conversion means, 6.
...beam splitter. Wow,

Claims (1)

[Claims] first and second optical frequency conversion means that are integrated on the same semiconductor substrate and have the same conversion characteristics for converting the amount of light into a frequency;
A comparing means for comparing the conversion frequencies of the first and second optical frequency converting means, an electro-optic converting means for changing the amount of output light according to the comparison result of the comparing means, and branching of the output light of the electro-optical converting means. and a beam splitter that outputs a part of the input light to the first optical frequency converting means and outputs the remaining light according to the amount of input light applied to the second optical frequency converting means. .